An "other" larger than about 1 1/2 GB usually indicates that the "other" includes corrupted files. Usually restoring from backup eliminated the corrupted files. However, sometimes restoring to factory settings/new iPod is required.
To restore from backup see:
To restore to factory settings/new iPod see:
see this discussion for suggestions:
i found that voice memos were the issue on mine, so if you have any apps that do recordings, use a program like DiskAid to see if you have a recordings stored on your phone, or check the apps that have recordings and delete them.